How to dynamically compose an OR query filter in Django?

问题

From an example you can see a multiple OR query filter:

Article.objects.filter(Q(pk=1) | Q(pk=2) | Q(pk=3))

For example, this results in:

[<Article: Hello>, <Article: Goodbye>, <Article: Hello and goodbye>]

However, I want to create this query filter from a list. How to do that?

e.g. [1, 2, 3] -> Article.objects.filter(Q(pk=1) | Q(pk=2) | Q(pk=3))

回答1:

You could chain your queries as follows:

values = [1,2,3]

# Turn list of values into list of Q objects
queries = [Q(pk=value) for value in values]

# Take one Q object from the list
query = queries.pop()

# Or the Q object with the ones remaining in the list
for item in queries:
    query |= item

# Query the model
Article.objects.filter(query)

回答2:

To build more complex queries there is also the option to use built in Q() object's constants Q.OR and Q.AND together with the add() method like so:

list = [1, 2, 3]
# it gets a bit more complicated if we want to dynamically build
# OR queries with dynamic/unknown db field keys, let's say with a list
# of db fields that can change like the following
# list_with_strings = ['dbfield1', 'dbfield2', 'dbfield3']

# init our q objects variable to use .add() on it
q_objects = Q()

# loop trough the list and create an OR condition for each item
for item in list:
    q_objects.add(Q(pk=item), Q.OR)
    # for our list_with_strings we can do the following
    # q_objects.add(Q(**{item: 1}), Q.OR)

queryset = Article.objects.filter(q_objects)

# sometimes the following is helpful for debugging (returns the SQL statement)
# print queryset.query

回答3:

A shorter way of writing Dave Webb's answer using python's reduce function:

# For Python 3 only
from functools import reduce

values = [1,2,3]

# Turn list of values into one big Q objects  
query = reduce(lambda q,value: q|Q(pk=value), values, Q())  

# Query the model  
Article.objects.filter(query)

回答4:

from functools import reduce
from operator import or_
from django.db.models import Q

values = [1, 2, 3]
query = reduce(or_, (Q(pk=x) for x in values))

回答5:

Maybe it's better to use sql IN statement.

Article.objects.filter(id__in=[1, 2, 3])

See queryset api reference.

If you really need to make queries with dynamic logic, you can do something like this (ugly + not tested):

query = Q(field=1)
for cond in (2, 3):
    query = query | Q(field=cond)
Article.objects.filter(query)

回答6:

See the docs:

>>> Blog.objects.in_bulk([1])
{1: <Blog: Beatles Blog>}
>>> Blog.objects.in_bulk([1, 2])
{1: <Blog: Beatles Blog>, 2: <Blog: Cheddar Talk>}
>>> Blog.objects.in_bulk([])
{}

Note that this method only works for primary key lookups, but that seems to be what you're trying to do.

So what you want is:

Article.objects.in_bulk([1, 2, 3])

回答7:

In case we want to programmatically set what db field we want to query:

import operator
questions = [('question__contains', 'test'), ('question__gt', 23 )]
q_list = [Q(x) for x in questions]
Poll.objects.filter(reduce(operator.or_, q_list))

回答8:

Using solution with reduce and or_ operator here how can you filter by multiply fields.

from functools import reduce
from operator import or_
from django.db.models import Q

filters = {'field1': [1, 2], 'field2': ['value', 'other_value']}

qs = Article.objects.filter(
   reduce(or_, (Q(**{f'{k}__in': v}) for k, v in filters.items()))
)

p.s. f is a new format strings literal aded in python3.6

回答9:

You can use the |= operator to programmatically update a query using Q objects.

回答10:

This one is for dynamic pk list:

pk_list = qs.values_list('pk', flat=True)  # i.e [] or [1, 2, 3]

if len(pk_list) == 0:
    Article.objects.none()

else:
    q = None
    for pk in pk_list:
        if q is None:
            q = Q(pk=pk)
        else:
            q = q | Q(pk=pk)

    Article.objects.filter(q)

回答11:

Another option I wasn't aware of until recently - QuerySet also overrides the &, |, ~, etc, operators. The other answers that OR Q objects are a better solution to this question, but for the sake of interest/argument, you can do:

id_list = [1, 2, 3]
q = Article.objects.filter(pk=id_list[0])
for i in id_list[1:]:
    q |= Article.objects.filter(pk=i)

str(q.query) will return one query with all the filters in the WHERE clause.

回答12:

easy..
from django.db.models import Q import you model args = (Q(visibility=1)|(Q(visibility=0)&Q(user=self.user))) #Tuple parameters={} #dic order = 'create_at' limit = 10

Models.objects.filter(*args,**parameters).order_by(order)[:limit]

来源：https://stackoverflow.com/questions/852404/how-to-dynamically-compose-an-or-query-filter-in-django

标签

python

django

django-q